Yarrow in Zone 4A — Great Plains

Yarrow is a fantastic addition to any Great Plains garden. It’s incredibly versatile, offering beautiful blooms for cutting and drying, attracting beneficial insects, and thriving in our challenging climate. Plus, its drought tolerance makes it a worry-free choice during our often-dry summers.

Our region is known for extreme weather, from spring temperature swings to the risk of hail and summer heat. But with a growing season of around 138 days, and careful timing, you can easily enjoy a bountiful harvest of yarrow.

Starting yarrow indoors gives you a head start, especially if you're aiming for blooms in the first year. It's best to sow seeds indoors from late February through mid March, about 8 weeks before you plan to transplant.

Use seed trays with a good seed-starting mix. Yarrow needs warmth and light to germinate, so a heat mat and grow lights are helpful. Bottom watering will prevent damping off and keep seedlings healthy. Keep in mind that our springs can be unpredictable, so indoor starting gives you a buffer against late frosts.

Transplant your yarrow seedlings outdoors from late April through late May, after the last expected frost. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week.

Space plants 12-18 inches apart. Choose a sunny spot with well-drained soil. Keep an eye on the weather forecast; even in late spring, we can get unexpected cold snaps, so be prepared to cover your young plants if needed. Since yarrow is a perennial, buying starts will give you flowers the first year.

Direct sowing is a viable option for yarrow, especially if you're not in a rush for first-year blooms. Sow seeds outdoors from early May through early July, when the soil has warmed up.

Prepare the soil by loosening it and removing any weeds. Yarrow prefers well-drained soil, so amend heavy clay soil with compost or other organic matter. Lightly cover the seeds with soil and keep them moist until they germinate. Thin seedlings to 12-18 inches apart.

Yarrow is incredibly drought-tolerant once established, making it perfect for our Great Plains climate. Overwatering leads to floppy growth and can even cause root rot, so less is definitely more.

During the first few weeks after planting, water regularly to help the plants establish a strong root system. After that, water only when the top 2 inches of soil feel dry to the touch – use the "finger test." Typically, established yarrow needs only about 1 inch of water per week, including rainfall. During periods of extreme heat or prolonged drought, you may need to water more frequently.

Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our low-to-moderate humidity. A light layer of mulch around the base of the plants will help retain moisture and suppress weeds.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can cause yellowing leaves and root rot. Adjust your watering schedule accordingly.

Deadheading is key to keeping your yarrow plants blooming throughout the season. Remove spent flowers as soon as they fade to encourage a second flush of blooms.

Throughout the summer, feel free to cut back stems for fresh or dried flower arrangements. In late fall, after the first frost around late September, cut the plants back to their basal foliage. Yarrow can be aggressive, so divide clumps every 2-3 years to prevent overcrowding.

You can expect your first yarrow harvest from mid July through early October, about 65 days after planting. Harvest the flowers for drying when they are fully open and the colors are vibrant.

Cut the stems just above a leaf node to encourage new growth. Hang the flowers upside down in a cool, dark, and dry place to dry them. Regular harvesting encourages continuous production throughout the season. As the first frost approaches, harvest any remaining blooms to dry indoors.

Here are some common problems you might encounter with yarrow in the Great Plains:

Aggressive Spreading

• What it looks like: Yarrow spreads quickly via rhizomes, forming dense colonies that can crowd out other plants.
• What causes it: Yarrow thrives in our fertile prairie soil and can become overly enthusiastic without intervention.
• How to fix/prevent it: Plant yarrow in a contained area or divide it regularly to keep it in check. Remove unwanted shoots as they appear.

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems. Leaves curl, yellow, and die.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it.
• How to fix/prevent it: Improve air circulation through spacing and pruning. Remove affected leaves. Neem oil or potassium bicarbonate sprays help. Milk spray (1 part milk to 9 parts water) is surprisingly effective.

Aphids

• What it looks like: Clusters of tiny soft-bodied insects (green, black, or white) on stems and leaf undersides. Sticky honeydew residue. Curled or distorted new growth.
• What causes it: Rapid-reproducing sap-sucking insects. Populations explode in warm weather. Ant colonies may farm them for honeydew.
• How to fix/prevent it: Strong water spray knocks them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap for heavy infestations. Neem oil works systemically. Avoid excess nitrogen fertilizer.

Great Plains Specific Challenges: Our extreme temperature swings and variable rainfall can stress yarrow, making it more susceptible to powdery mildew. The hot summer heat can also encourage aphid infestations. Monitor your plants regularly and take action promptly to prevent problems from escalating.

Yarrow is a wonderful companion plant for many vegetables and herbs in the Great Plains garden. It attracts beneficial insects like ladybugs and lacewings, which prey on pests that can damage your crops.

Good companions include:

• Tomatoes and peppers: Yarrow helps repel pests that attack these plants.
• Herbs: Yarrow enhances the flavor and growth of many herbs.
• Strawberries: Yarrow attracts beneficial insects that pollinate strawberries.

Avoid planting yarrow near plants that prefer very rich soil and consistent moisture, as yarrow thrives in drier, less fertile conditions.